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Remediation of PCB-contaminated soils. Risk analysis of biological in situ processes

Abstract

Biological in situ measures can be efficient and cost effective options for the remediation of contaminated sites. However, the accepted application requires a detailed and reliable analysis of potential impacts. An important objective is to quantify the potential of contaminant degradation and metabolite formation. This thesis addresses a quantitative multimedia risk assessment. Methodologies and tools were developed for this objective and applied to evaluate in situ bioremediation of soils contaminated with polychlorinated biphenyls (PCBs). Soil bacteria in conjunction with plant roots were addressed (rhizoremediation) with a focus on the use of genetically modified microorganisms (GMOs). PCBs are known to be harmful compounds that are ubiquitously distributed in the environment. PCB contaminations in soil and groundwater were identified as important problems. 209 different congeners are sterically possible, but not all are of environmental significance. PCB congeners of concern were evaluated with respect to their potential toxicity, environmental occurrence and mobility. For this objective, congener specific data on the toxicity potential and the frequency in environmental matrices were collected. To quantify the mobility potential, multimedia modelling was performed applying deterministic and probabilistic procedures. 56 PCB congeners of concern were evaluated, and multimedia risk assessments of PCB-contaminated soils should concentrate on this group.  More>>
Authors:
Publication Date:
Dec 08, 2006
Product Type:
Thesis/Dissertation
Report Number:
ETDE-DE-2199
Resource Relation:
Other Information: TH: Diss. (Dr.rer.nat.); Related Information: Tuebinger geowissenschaftliche Arbeiten , TGA: Reihe C, Hydro-, Ingenieur- und Umweltgeologie v. C102
Subject:
54 ENVIRONMENTAL SCIENCES; BIODEGRADATION; BIOREMEDIATION; KINETICS; METABOLITES; MICROORGANISMS; POLYCHLORINATED BIPHENYLS; RISK ASSESSMENT; SURFACE CONTAMINATION
OSTI ID:
21277881
Research Organizations:
Tuebingen Univ. (Germany). Geowissenschaftliche Fakultaet
Country of Origin:
Germany
Language:
English
Other Identifying Numbers:
Other: ISSN 0935-4948; TRN: DE10G2728
Availability:
Commercial reproduction prohibited; OSTI as DE21277881
Submitting Site:
DE
Size:
203 pages
Announcement Date:
Mar 27, 2010

Citation Formats

Rein, Arno. Remediation of PCB-contaminated soils. Risk analysis of biological in situ processes. Germany: N. p., 2006. Web.
Rein, Arno. Remediation of PCB-contaminated soils. Risk analysis of biological in situ processes. Germany.
Rein, Arno. 2006. "Remediation of PCB-contaminated soils. Risk analysis of biological in situ processes." Germany.
@misc{etde_21277881,
title = {Remediation of PCB-contaminated soils. Risk analysis of biological in situ processes}
author = {Rein, Arno}
abstractNote = {Biological in situ measures can be efficient and cost effective options for the remediation of contaminated sites. However, the accepted application requires a detailed and reliable analysis of potential impacts. An important objective is to quantify the potential of contaminant degradation and metabolite formation. This thesis addresses a quantitative multimedia risk assessment. Methodologies and tools were developed for this objective and applied to evaluate in situ bioremediation of soils contaminated with polychlorinated biphenyls (PCBs). Soil bacteria in conjunction with plant roots were addressed (rhizoremediation) with a focus on the use of genetically modified microorganisms (GMOs). PCBs are known to be harmful compounds that are ubiquitously distributed in the environment. PCB contaminations in soil and groundwater were identified as important problems. 209 different congeners are sterically possible, but not all are of environmental significance. PCB congeners of concern were evaluated with respect to their potential toxicity, environmental occurrence and mobility. For this objective, congener specific data on the toxicity potential and the frequency in environmental matrices were collected. To quantify the mobility potential, multimedia modelling was performed applying deterministic and probabilistic procedures. 56 PCB congeners of concern were evaluated, and multimedia risk assessments of PCB-contaminated soils should concentrate on this group. Kinetics parameters were specified for degradation experiments with individual PCB congeners in solution and different bacterial strains. These laboratory assays were performed with wild-type Burkholderia sp. strain LB400 and the genetically modified Pseudomonas fluorescens strains F113pcb and F113L::1180. The F113 derivatives demonstrated a good survival ability in willow (Salix sp.) rhizosphere (mesocosm experiments). Therefore, and due to high depletion rates, rhizoremediation with F113L::1180 and willow plants might be a promising approach. Degradation kinetics in soil was estimated, but it is associated with a high uncertainty. The relation of degradation kinetics in laboratory (solution) to field conditions (soil) necessitates further research. Results of exemplary modelling were sensitive to estimated removal velocities, and especially to variable bacterial numbers in soil. A multimedia model was set up to estimate biodegradation and metabolite formation, fate and transport of contaminants and risks arising from the exposure to contaminated media. With this model, deterministic and probabilistic calculations (performing Monte Carlo simulations) were carried out to generically evaluate rhizoremediation of PCB contaminated soil. Results indicate a clear potential for risk reduction associated to the use of F113L::1180 and willow plants. PCB was effectively reduced by the investigated strains but nonetheless, chlorobenzoic acids (CBAs) as degradation products of concern revealed a high importance for the aquatic pathway (leaching, groundwater transport, mixing with surface water) and the uptake into plants. Thus, drinking water wells should be located in a sufficient distance to the source (5 km at least as a conservative estimate for the studied scenario). However, high uncertainty remains for the degradation potential of PCB mixtures in soils. Risks associated to the investigated GMOs are expected to be very low. Results of laboratory experiments with F113 derivatives and field release tests with non-GM F113 strains gave no significant hint on uncontrolled bacterial spreading. Observed gene transfer rates were very low, as the introduced bph trait is stably inserted into the chromosome of F113. Potential impacts of GMOs on microbial soil communities also were very low, but there was a shift in rhizosphere populations. Uncertainty is given for possible long-term effects, especially for gene transfer processes and impacts on soil bacteria, and for potential adverse effects on other soil organisms. Potential field release applications of in situ bioremediation using GMOs require performance control in the source zone (to ensure the functionality of the degradation process) and compliance monitoring, addressing contaminants, metabolites and GMOs. Detailed guidelines were compiled for respective tasks. (orig.)}
place = {Germany}
year = {2006}
month = {Dec}
}